1. Field of the Invention
The invention relates to a motor vehicle door lock having a lock carrier such as a housing or lock plate, a rotary latch in the form of a disk with a receiving opening for a key collar or a locking pin, and with a detent pawl for locking the rotary latch in a locked position which corresponds to a closed motor vehicle door.
2. Description of Related Art
Classical motor vehicle door locks use a rotary latch which is made as a fork latch, which is made solid, and which is pivotally mounted as a swivel axle on a journal which is fixed in the housing or on the lock carrying plate published German Patent Application Nos. -A-29 36 997, DE-A-32 42 527). In the closed position of the motor vehicle door the fork latch secures the forward leg of a key collar or a locking pin with the receiving opening so that the motor vehicle door cannot spring open even when high tearing forces occur in a crash. The fork latch itself is fixed in this closed position by a detent pawl which is tensioned or compressed via locking surfaces which engage one another (main catch).
In the above explained known construction the tearing forces in case of a crash engage the rotary latch via a relatively large lever arm and the latch must be made rather bulky. The same applies to the detent pawl which holds the rotary latch and which must accommodate most of the tearing forces as a result of the existing lever ratios.
The prior art discloses, as an alternative to a fork latch, making the rotary latch as a disk of solid material published German Patent Application No. -C-16 78 121). In this case, the rotary latch is pivotally supported in a recess which has a peripheral surface which adjoins the rotary latch and forms the guide of the latter. A journal which forms the swivel axle is not present in the middle of the rotary latch. The swivel axle of the rotary latch is only virtually formed. The rotary latch is fixed axially by the bottom surface of the recess and by a cover, in the area of the center point of the rotary latch on the cover there being an impression which limits the sliding friction between the rotary latch and the cover at the center point. The lever ratios in this alternatively built rotary latch are in principle for the most part exactly as in the above explained fork latch.
Rotary latches, especially in the form of fork latches, have already been made as composite parts from metal and plastic published German Patent Application No. -A-06 69 437). This is done primarily by a base body which represents the fork latch itself being made of metal which is then provided with a plastic extrusion coating. This is intended to form the bearing, attenuate noise, prevent metal/metal contact, etc. In the course of extrusion coating with plastic in particular recesses can also be made especially on the peripheral surface of the rotary latch either to make elastic attenuation buffers or to be able to execute switching functions in conjunction with microswitches in the housing of the motor vehicle door lock. Other areas, especially areas which in case of a crash are exposed to high tearing forces, in the meantime remain free of the plastic jacketing. This applies especially to the main catch of the rotary latch on which the detent pawl keeps the rotary latch in the closed position.
Generally, in the prior art it is found that the locking parts, i.e. the rotary latch and the detent pawl, as in the other areas of the motor vehicle door lock, are designed for crashes; this entails over dimensioning and in any case is not an optimal configuration for the normal case of operation. For example, in the rotary latch this means that in it there is a bearing opening for the bearing pin which is fixed on the housing, which forms the swivel axle, and which has a large diameter designed for crashes. The rotary latch itself is however relatively narrow, and is generally only a few millimeters wide. The bearing surface on the bearing pin which forms the swivel axle is therefore rather narrow. A lateral inclination of the rotary latch in the case of a crash under the action of high tearing forces therefore represents a major problem. This problem has been recognized and has lead to the rotary latch being coupled in the axial direction to the detent pawl by profiling in the engagement area published German Patent Application No. -A-18 12 528).
The aforementioned makes it clear that the rotary latch as one of the most important parts of a motor vehicle door lock or the like has not been adequately analyzed so far with respect to the stress field between operating safety (especially in case of a crash) on the one hand and production cost on the other.
The similar applies to the detent pawl of the known motor vehicle door locks or the like. It is generally swivel mounted on a bearing pin which is parallel to the bearing pin of the rotary latch. All the tearing forces in case of a crash, to the extent they are diverted via the detent pawl, are diverted by the detent pawl into the bearing pin and from there into the housing or the lock carrying plate. This is independent of whether the detent pawl is tensioned or compressed.
The aforementioned makes it clear that in existing motor vehicle door locks the optimized configuration of the locking parts, i.e. the rotary latch and the detent pawl, has not yet been adequately considered. This has led to the fact that the rotary latch and the detent pawl have been more and more dramatically overdimensioned with increasing demands for operating safety, especially operating safety in case of a crash. Attempts have been made to accommodate the tearing forces in case of a crash by a large undercut angle between the detent pawl and the rotary latch. This in turn has had an adverse effect on the opening forces between the rotary latch and the detent pawl.